A major gap in our knowledge of violence perpetration concerns the way in which social and physiological risk factors relate in predisposing to violence. Specifically, the interaction between social and physiological factors may better explain violence perpetration than either factor alone. This study aims to attempt a genuine integration of social and physiological approaches in order to help develop a new knowledge base on the perpetration of violence. Three physiological theories of violence, namely, arousal theory, stress reactivity theory, and frontal lobe dysfunction theory, will be used to help guide this research. Some of the main questions to be addressed concern how social and physiological risk variables interact, how these variables can explain maintenance of violent behavior over time, and whether subjects who possess social risk factors are protected from perpetrating violence by virtue of possessing physiological protective factors. These questions will be addressed by a reassessment of 508 boys in the Pittsburgh Youth Study who have already been longitudinally assessed from ages 10 to 14 on an extensive set of family, school, attitude, peer, neighborhood, delinquency, psychopathology, impulsivity, self-report and official delinquency measures. New social and behavioral data will be collected at age 18 together with psychophysiological, hormonal, and neuropsychological assessments to help address the above questions. Frontal dysfunction theory will be used to provide an overall theoretical framework. It is felt that the Pittsburgh Youth Study offers a potentially unique opportunity to conduct a multidisciplinary project on the confluence of social and physiological risk factors for the development of violence perpetration.